1. Field of the Invention
The invention relates to surgical instruments for withdrawing or introducing fluids into the body and more particularly to venous catheters.
2. Description of the Related Art
Development in the technology and instruments for intravenous therapy has been spurred by increasing needs for effective, long-term access to major veins and arteries. Increased use of hemodialysis, chemotherapy, hyperalimentation and the growing number of patients requiring frequent venous access, have resulted in a refinement of catheter devices for intravenous therapy. Commercially available devices include the Hickman Catheter (trademark), Raff Catheter (trademark) and Broviac Catheter (trademark). A more recent improvement over prior devices is the Groshong Catheter (trademark). Generally, these devices use a flexible catheter having single or multiple lumens. The cannula is inserted into the subclavian vein under the collarbone and led along the vein into the very large vein entering the heart, the vena cava superior. The access to the vena cava is required so that concentrated solutions being introduced into the patient will be rapidly diluted thereby avoiding the severe pain, vein inflammation and possible thrombosis associated with intravenous therapy using smaller veins located in the arms or legs. Hyperalimentation, or total nutritional support via intravenous transfer, precludes the use of small veins. Despite the resolution of thrombosis, and related difficulties, complications remain in the intravenous therapy procedures. The puncture at the proximal end or entrance point on the surface of the skin remains a primary source of infection. (Throughout this application, the word "proximal" will refer to the near end or surface end of the catheter or sheath where it normally attaches to the skin, and the word "distal" will refer to the far end, closer to the heart.) The hardware and tubing protruding from the patient's body not only provide a source of infection, but also expose the patient to potentially serious injuries in the event of an accidental dislodgment of the mechanism. Additionally, the hardware and associated protrusions are cosmetically unappealing and limit the patient's physical mobility.
Other problems with current catheters include clotting problems particularly where blood may clot in the distal end of the catheter, thereby requiring removal and replacement of the entire catheter. Some catheters must be flushed as often as every eight hours with an anticoagulant such as heparin. The major shortcomings of the current catheter hardware result from the permanent implantation of the catheter in the blood stream. Because of the permanent presence in the blood stream, a multitude of difficulties arise. The catheter itself is subject to clotting along the outer surface and clotting and obstruction within the lumen. Also, during intermittent intravenous therapy, such as that typical of home hyperalimentation, the entire internal surface of the catheter is filled with solution providing a "wet" environment likely to support fungal or bacterial growth. This risk is especially high where blood clots form around slit-style valves.
As the catheter is permanently implanted, cleaning by flushing with an anticoagulant solution is the only practical method of maintaining the patency of the device when flushing fails, surgical removal is the only alternative.
Further, dangers of fatal air embolism are present during surgical insertion and removal, and whenever the catheter is installed. Physical damage to the proximal end may dislodge the catheter or cause a break in the catheter with the potential result of an embolism. Similar physical damage may dislodge the catheter allowing it to migrate further into the vena cava. Finally, despite the permanent insertion of the catheter, replacement is necessary at frequent intervals to avoid infection, contamination and blockage by clotting. Accordingly, it is an object of the present invention to provide means to permit multiple, non-traumatic insertions and removals of intravascular catheters.
Another object of the present invention is to provide a positive mechanical valve for the distal end of a catheter assembly.
It is yet another object of the present invention to provide a dry environment for the catheter cannula.
Still another object of the present invention is to provide a catheter apparatus for intravenous therapy which will substantially reduce the risk of loss of blood and the risk of air embolism
Yet another object of the present invention is to provide a catheter apparatus for intravenous therapy which will not require anticoagulant flushing.
A further object of the present invention is to provide a catheter apparatus for intravenous therapy which will substantially reduce the risk of infection
It is still a further object of the present invention to provide a sheath-catheter combination which will allow ready removal of the catheter leaving the sheath in place to provide a repeated access for long term intravenous therapy.
It is another object of the present invention to provide a catheter entry means at the skin surface which is cosmetically and functionally designed to eliminate protruding tubing and hardware.